1. Field of the Invention
The present invention relates to a bicycle wheel rim, more particularly to a bicycle wheel rim capable of effectively preventing disengagement of a bicycle tire therefrom.
2. Description of the Related Art
As shown in FIG. 1, a first conventional bicycle wheel rim includes an annular rim body with spaced-apart left and right tire retaining walls 12 and a spoke mounting wall 11 interconnecting the tire retaining walls 12. The spoke mounting wall 11 is formed with a plurality of angularly displaced spoke mounting holes 15 which are arranged along the length of the spoke mounting wall 11 for retaining spoke fasteners 16 of spokes 10 therein. The tire retaining walls 12 and the spoke mounting wall 11 cooperatively confine a tire retaining space 14 for retaining a bicycle tire 1 therein. The bicycle tire 1 typically includes an inflatable inner tire body 17 and an outer tire body 18 enclosing the inner tire body 17. A lining 19 is disposed between the inner tire body 17 and the spoke mounting wall 11 to protect the inner tire body 17 from being pierced by the spoke fasteners 16. When the inner tire body 17 is inflated after installation of the inner and outer tire bodies 17, 18 on the wheel rim 1, the outer tire body 18 is stretched to engage two opposite hooked edges 181 thereof with hooked radial outer edges 13 of the tire retaining walls 12. However, once the inner tire body 17 is accidentally deflated, or in the case the inner tire body 17 is not fully inflated, the opposite hooked edges 181 of the outer tire body 18 could be easily disengaged from the radial outer edges 13 of the tire retaining walls 12.
FIGS. 2 and 3 illustrate another conventional bicycle wheel rim 2 suitable for use with a bicycle tire which includes only an outer tire body 20 and which is free of an inner tire body. The bicycle wheel rim 2 includes annular left and right tire retaining walls 23 spaced apart from each other, a spoke mounting wall 21 interconnecting radial inner edges of the tire retaining walls 23, and an annular connecting wall 26 disposed around the spoke mounting wall 21 and extending between intermediate sections of the tire retaining walls 23. A tire retaining space 24 is formed among the connecting wall 26 and tire retaining walls 23. To facilitate installation of the tire body 20, the connecting wall 26 is configured to have a central indented portion 261 that is indented in a radial inward direction to define an annular recess 22. During installation, two confronting edge portions 201 of the tire body 20 are extended into the recess 22 so as to be temporarily retained therein. Thereafter, high pressure air is pumped into an interior of the tire body 20 to inflate the same. At this time, the edge portions 201 are forced to move away from each other and move out of, the recess 22 so as to engage radial outer edges 25 of the tire retaining walls 23, respectively. However, since the tire body 20 engages the recess 22 before inflation, high pressure air is required to inflate the tire body 20. The bicycle wheel rim 2 is still not satisfactory.
Therefore, the main object of the present invention is to provide a bicycle wheel rim capable of effectively preventing disengagement of a bicycle tire therefrom.
Accordingly, the bicycle wheel rim of the present invention includes an annular rim body with a central axis. The rim body has annular left and right tire retaining walls, an annular spoke mounting wall, and a tire retaining cavity. The tire retaining walls are spaced apart from each other. Each of the tire retaining walls has a radial inner edge proximate to the central axis of the rim body, and a radial outer edge distal to the central axis of the rim body. The spoke mounting wall interconnects the radial inner edges of the tire retaining walls, and is formed with a set of spoke mounting holes adapted for retaining spoke fasteners therein. The tire retaining cavity is formed between the tire retaining walls, and is configured to have two opposite lateral cavity parts proximate to the tire retaining walls, respectively, and an intermediate cavity part between the lateral cavity parts. The lateral cavity parts are deeper than the intermediate cavity part with respect to the radial outer edges of the tire retaining walls.